The production of ionized particles is well known from the literature, particularly in the field of electrostatic and electro-thermal propulsion systems for space applications.
For example, electrostatic devices follow the functional principle that a gaseous propellant is ionized with the aid of an ionization source. An ion extraction device produces a beam of positive ions out of the existing-plasma. A voltage control unit can be used to adjust the potential of the voltage between the shield electrode and the acceleration electrode to provide a level of variability to the impulse of the ions, but not the mass or nature of the ions produced.
Likewise, electro-thermal particle systems generate a hot exhaust gas by the combustion of a propellant inside a combustion system. This gas can then be partially ionized to form a plasma. Again, the superposition of an electric field can produce an additional variable impulse, but cannot change the mass or nature of the particles produced in the exhaust gas.
Numerous additional examples exist. Plasma accelerators, for example, follow the functional principle that a propellant gas (e.g., helium or xenon) is introduced into the acceleration chamber and, in a first step, (partially) ionized. The ionization can be carried out with the aid of helicon-antennas, microwave induction, radio frequency or electron bombardment. There is no macroscopic separation of electrons and ions. The plasma is accelerated with electric and magnetic fields. The magnetic field further serves to focus the ionized gas stream and produce an electron cyclotron resonance (ECR) or ion cyclotron resonance (ICR) movement. The electrons move in opposition to the ions. Due to the scattering of electrons with neutral gas atoms or molecules there is a secondary ionization reaction with leads to an increase in the total ionization of the plasma. A special development of a plasma propulsion system is the Hall-Thruster, which is characterized in e.g., U.S. Pat. No. 5,845,880.
There has also been quite a significant level of interest in providing systems which allow for a variable specific impulse from the generated particles. For example, in U.S. Pat. No. 6,334,302 a two stage accelerator is provided. In this system, a propellant (hydrogen, methane or ammonia) is introduced to a first system stage where it is ionized via a helicon antenna. The ionized gas forms a plasma that is then accelerated via an electrostatic field. The gas then enters a part of the propulsion chamber where it is further heated via superconducting magnets. This part of the propulsion system could be called ICR-chamber. A disadvantage of the disclosed plasma accelerator is the use of a propellant with a relatively small molecular mass. Therefore specific impulse and thrust can be varied only within narrow limits.
Likewise, U.S. Pat. No. 5,170,623 discloses a hybrid chemo-electrical propulsion system. Inside a combustion chamber a propellant is oxidized and expanded via a nozzle. Outside of the diffuser a coil is arranged. The hot partially ionized exhaust gas stream is superposed and accelerated by a magnetic induction field. The variable electromagnetic field which is induced by the coil leads to a further ionization. Ions become magnetically accelerated with a specific impulse between 800 and 2500 s. A disadvantage of this propulsion system is the separation of chemical reaction chamber and acceleration system inside the diffuser.
Despite the significant level of interest in ionized particle generators, no system has been designed that would allow for the variability of particle size and mass. Accordingly, a need exists for an improved particle generator for producing ionized nanoparticles of a defined mass as well as a variable specific impulse